The embattled Cadbury confectionery empire faced a takeover siege on multiple fronts today as Italy's Ferrero and the US chocolate firm Hershey declared that they were considering competing with Kraft's £9.8bn takeover offer for the 185-year-old maker of Dairy Milk bars, Creme Eggs and Trident chewing gum.

Ferrero and Hershey released separate statements formally confirming that they were reviewing options towards Cadbury. Although they gave no indication of working together, sources close to the two firms say that they have discussed combining their financial firepower to launch a joint offer for the British company.

Both are substantially smaller players than Kraft, the world's second-largest food company, which tabled a 717p-a-share bid for Cadbury last week, and there was scepticism both in the City and on Wall Street about their prospects of muscling in.

Analysts pointed out that they would need to raise substantial debt for a cash offer and that there were likely to be clashes over the spoils, with ownership of Cadbury's chocolate business attractive to both Ferrero and Hershey.

Cadbury, which rebuffed Kraft's offer as "derisory" last week, made it clear it would prefer to remain independent: "We're focused on delivering value to shareholders as a standalone pure-play confectioner." But the company, which saw its shares jump by 9.5p to 797.5p, added: "We have always said that we would give proper consideration to any serious offer that delivers full value for the company. Unless and until we find ourselves in that situation we have nothing to comment upon."

Ferrero is known for its Nutella spread, Tic Tac mints and Ferrero Rocher chocolates and is controlled by its founding family, headed by 84-year-old Michele Ferrero, a Monte Carlo-based patriarch who is ranked by Forbes magazine as Italy's richest man with a fortune of $9.5bn (£5.7bn).

Meanwhile Pennsylvania-based Hershey has a stock market listing but a charitable foundation, the Hershey Trust, owns a controlling stake.

Tom Groves, a food industry analyst at Standard & Poor's in New York, said geographical diversification was at the heart of Cadbury's appeal.

The British company's strong brand in emerging markets, including India and parts of Africa, gives it an attractive position for long-term growth: "We should see increasing demand for chocolate as we see an emerging middle class in developing countries. Chocolate and candy will become more popular products."

There was surprise in the US that Hershey, long seen as a relatively conservative player, was willing to wade into a competitive struggle for control.

Hershey owns a licence to make Cadbury's chocolate in the US, although it uses a different recipe to suit American tastes and its output of Cadbury-branded products is relatively limited.

Barclays Capital analyst Justin Ong said Ferrero and Hershey could either table a bid envisaging a carve-up of Cadbury or they could create a joint ownership structure. A third option, he suggested in a research note, would be for them to make a "white knight" approach creating an alliance with Cadbury to stave off Kraft: "Should Ferrero and Hershey decide on a financially credible counterbid for Cadbury, this would step up the pressure on Kraft to improve the size and cash proportion of its offer."

Kraft's bid is for a combination of 300p in cash and 0.25 of its US shares for each Cadbury share. Advisers to Kraft say that its rationale for a combination is superior to the logic offered either by Ferrero or Hershey, with $625m in potential annual cost savings, plus complementary distribution channels – Kraft is stronger in China, Brazil and Russia.

But union officers, already worried at the prospect of huge job cuts by Kraft, still believe that independence would be the best outcome for Cadbury's 46,000 employees.

Jennie Formby, national officer for food and drink at Unite, said: "Any company that's looking to buy Cadbury would be looking to make cost savings to help finance their bid."